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Influence of stimulus parameters on human postural responses
H C Diener1, F B Horak, L M Nashner
1Neurological Sciences Institute, Good Samaritan Hospital and Medical Center, Portland, Oregon 97209.
Journal of Neurophysiology
|June 1, 1988
Summary
Sensory information adjusts muscle activation intensity for postural control. Response patterns are independent of stimulus intensity but scale with velocity and amplitude for effective balance.
Area of Science:
- Neuroscience
- Biomechanics
- Human Movement Science
Background:
- Postural control relies on sensory feedback to adjust muscle activity.
- Understanding how sensory information modulates automatic postural responses is crucial.
Purpose of the Study:
- To investigate the role of sensory information in shaping muscle activation patterns during postural perturbations.
- To examine how perturbation velocity, amplitude, and duration influence kinematic and electromyographic (EMG) responses.
Main Methods:
- Ten healthy subjects underwent backward translations of the support surface with varied velocities, amplitudes, and durations.
- Movement kinematics and EMG activity in six trunk and leg muscles were recorded and analyzed.
- EMG data were normalized, and early, middle, and late components were analyzed separately.
Main Results:
- A consistent movement strategy scaled with perturbation velocity and amplitude.
- Short-duration perturbations (<75 ms) elicited a fixed muscle response, independent of stimulus parameters.
- For longer perturbations, muscle activation intensity correlated with stimulus velocity and amplitude, particularly in later EMG components.
Conclusions:
- Automatic postural response organization is spatially and temporally independent of response intensity.
- Sensory information specifying perturbation velocity and amplitude adjusts the magnitude of muscle activation within a set pattern.